Add a (require 'notmuch-message) to notmuch.el. This is for functions that
specifically target message mode (and, in the future, notmuch-message
mode).
(require 'notmuch-mua)
(require 'notmuch-hello)
(require 'notmuch-maildir-fcc)
(require 'notmuch-mua)
(require 'notmuch-hello)
(require 'notmuch-maildir-fcc)
+(require 'notmuch-message)
(defcustom notmuch-search-result-format
`(("date" . "%s ")
(defcustom notmuch-search-result-format
`(("date" . "%s ")